I've done the file xfer thing from Windows 10 to my armada of oldschool PC's ranging from a Tandy 1000A running DOS 6.22 to my Pentium 100 NEC running Windows 98 SE. Typically the method depends on the devices OS.
For official Microsoft O/S, such as DOS or Windows 3.11 For Workgroups, or Windows 9x, or 2000, I have to change some settings on the Windows 10 box which by modenr security standards DO make the machine less secure. I have to enable SMB 1.0 (Win10 turns it off by default as a security measure), enable the windows 10 box to send unencrypted passwords to 3rd party SMB servers, and then do all of my mapping using win+R \\sharename or right clicking on Networks in Windows Explorer and then putting the sharename in. I don't like the lack of security it introduces but such is the risks of dealing with Microsoft products that are older than 7 in 2020.
Another option, particularly my favourite for DOS (usually FreeDOS 2.x) , is to temporarily setup a FTPServer on the old box with mTCP and then use an FTP Client on the machine that has the files I want to send on it. Much more secure as the network interface for the old machine is only active when it's in use.. TBH, I'm getting a bit more favouring toward FreeDOS most of the time on my vintage machines these days. Another nice thing with FreeDOS is on 386 or newer hardware you can use the text based browser Links to download stuff from the internet directly like you would with Firefox or Chrome so if you are getting something else, like drivers, or freeware, or whatever, the DOS Box can be used to download it itself with no modern device required.